In the enzymatic reaction, H-protein activates the P-protein, which catalyzes the decarboxylation of glycine and attaches the intermediate molecule to the H-protein to be shuttled to the T-protein.[4][5] The H-protein forms a complex with the T-protein that uses tetrahydrofolate and yields ammonia and 5,10-methylenetetrahydrofolate. After interaction with the T-protein, the H-protein is left with two fully reduced thiol groups in the lipoate group.[6] The glycine protein system is regenerated when the H-protein is oxidized to regenerate the disulfide bond in the active site by interaction with the L-protein, which reduces NAD+ to NADH and H+.